The avain erythroblastosis virus, E26, is a replication-defective retrovirus which causes erythroblastosis and myeloblastosis in chickens. The transforming gene of E26 includes elements from two proto-onc genes, chicken proto-myb and chicken proto-ets, and Deltagag from the viral gag gene. Human genomic clones homologous to the ets region of the E26 virus were molecularly cloned and shown to be closely related to the v-ets region by hybridization and partial sequence analysis. The human ets DNA is located on two different chromosomes. The human ets-1 locus on chromosome 11 encodes a single mRNA of 6.8 kb; the second ets-2 locus on chromosome 21 encodes three mRNAS of 4.7, 3.2 and 2.7 kb. In order to study the structural organization and splicing mechanism of the human ets-1 and ets-2 genes, a cDNA library was prepared from a human COLO 320 cell line which expresses very high levels of ets-specific transcripts. Several recombinant clones reactive with ets-1 and ets-2 probes were isolated. These cDNA clones are being characterized by restriction mapping and Southern blot analysis into a different family of mRNAs. These clones are also being sequenced. There is preliminary evidence to state that these multiple transcripts, in the case of ets-1 and ets-2, may have been generated through alternative splicing events. The full legnth cDNA clones of ets-1 and ets-2 are being expressed in vitro and in in vivo in E. coli and in mammalian cells. With the above study, it may become possible to define precisely any small differences between the viral genes and their cellular counterparts--differences that may be crucial for the regulation of the "genes" expression or the range of their biological functions. These regulatory genes, which have been conserved during evolution, may have some role in cell differentiation and multiplication.